System of compensation



March 22, 1938. y i. D. APPLEGATE 2,112,058

SYSTEM OF COMPENSATION `Filed Jan. 16, 1956 WITNESSES: aNvENToR C? af? /Jp/eyaike I L W BY To-RNEY Patented Mar. 22, 1938 UNITED STATES PATENT FFICE SYSTEM 0F COMPENSATION of Pennsylvania Application January 16, 1936, Serial No. 59,403

l2 Claims.

My invention relates to compensating means adapted for use with indicating devices and automatic regulators and has particular relation to line drop compensators associated with three- 5 phase transmission and distribution circuits.

Automatic voltage regulators and indicating devices are frequently located at some distance from the point or" power distribution at which it is desired that the voltage be maintained conm stant, and for this reason it is necessary to provide means for compensating their operation in accordance With the voltage drop in the feeder circuit. The total voltage drop varies with the current flowing in the circuit and is the vector 15 sum of the resistance and reactance components of voltage drop through the circuit impedance.

To effect compensation, a device known as a line-drop compensator is employed in the control circuit oi the regulator operating means.

Such a compensator duplicates the line drop Voltage between the point in the power circuit to which the voltage responsive element is connected `and the point in the circuit at which it is desired the voltage responsive element should respond, and introduces this voltage drop component into the voltmeter energizing circuit. Through it a current is passed that is proportional to the line current and which causes a voltage drop across it that is proportional to the voltage drop in the line.

In the application of polyphase-controlled voltage regulators to three phase circuits, it is further essential, especially when large compensation is needed, that there be provided a compensated control potential which is representative of the voltages acting in all three of the circuit phases, otherwise for conditions ci circuit unbalance, the regulator operation will not be coincident with the actual circuit requirements. ,40 To obtain representative indications of the type above discussed it has been necessary to employ three single-phase compensator assemblages, each of which involves a resistance element, a reactance element, an energizing current transformer and other comparatively expensive equipment. For some time attempts have been made to obtain equivalent results by the use of only two compensator equipments, however, within my knowledge all of these have failed in one or more important particulars.

Generally stated, the object of my invention is to reduce the cost of the apparatus required to accurately compensate the control oi regulators for three-phase circuits under changing conditions of load, power factor, voltage and the like.

(Cl. .N1- 119) A more specic object is to achieve the abovea stated results through the use of only two singie-phase compensator assemblages.

An additional object is to provide a system of interconnection for the resistance and reactance elements of compensators associated with but two oi the three phases of the regulator circuit which provides a three phase potential compensated for line drop in a symmetrical or balanced ianner for changing conditions of circuit load and power factor.

In practicing my invention, I connect in each of two ol the three conductors which supply control potential to the regulator a single phase conn pensator assemblage including both resistance and reactance elements. I then energize each of these by a measure of the current in the conductor of the regulated circuit corresponding to the phase with which the other compensator is associated. By means of this cross-energizing connection, and a reversal oi certain oi the eieh ment output connections, I am able to so modify the voltages in two of the phases oi the control supply circuit for the regulator that the resultant potentials in all three phases of this circuit accurately correspond at al1 times and under all conditions to the requirements at the distant point in the regulated circuit at which the regulator is intended to maintain constant Voltage.

My invention, together with additional objects and advantages, will best he understood through the following description of a specic embodiment when taken in conjunction with the accompanying drawing, in which Figure l is a diagrammatic View of apparatus and circuits illustrating the simplied compensating System of my invention appli-ed to an automatic voltage regulator for a three-phase transmission circuit, and

Fig. 2 is a diagram of vectors illustrating the mode of operation oi" my improved form oi compensator element connections.

Referring to the drawing, I have illustrated in Fig. l the improved system of my invention as being combined with the control supply circuits of a voltage-adjusting equipment or regulator i6 associated with a three-phase transmission circuit which comprises line conductors A, B and C which terminate at a point distant from the regulator. tional manner by means of a Contact making voltmeter or primary relay l2 which is responsive to changes in the voltage of the regulated circuit. The actuating winding I4 of this relay is supplied, through a connection which includes a This equipment is controlled in convenpair of potential transformers IS and a plurality of rectifiers I8, with a measure of the voltage of regulated circuit A-B-C.

In the operation of this regulating system, as long as the voltage of the regulated circuit remains at the desired value, the representative potential Ek impressed upon the primary relay I2 maintains the movable contact member 20 thereof in the disengaged or mid-position illustrated. Under this condition, no operation of the regulator I0 takes place. When, however, the circuit Voltage drops, the resulting decrease in relay potential Ei; causes contact member 20 to move upwardly and engage the raisey stationary member to thereby correctively operate the equipment I0 in the circuit voltage raising direction. In a similar manner a rise above the desired value moves member 20 downwardly into engagement with the lower stationary member which correctively operates the regulator I0 in the circuit Voltage lowering direction.

For the purpose of modifying the three phase control potential impressed through the rectifiers I8 upon the primary relay I2, I connect in two of the conductors of the control supply circuit single-phase compensator assemblages generally indicated at 22 and 24. Each of these assemblages comprises a reactance-compensating element, in the form of a resistor 26 which may, as shown, have an insulating transformer 28 connected thereacross, and a resistance-compensating element in the form of an air-gap core type of reactor 30. It will be noted that in the system of my invention the resistance and reactance element structures are interchanged with respect to those of the usual arrangement.

The compensator 22 which is connected in the conductor 32 of the regulator supply circuit (corresponding to the phase conductor B of the regulated circuit) is energized through a current transformer 34 by a measure of the current Ib flowing in the regulated circuit conductor C. Similarly, the compensator 24 connected in conductor 36 of the regulator supply circuit (corresponding to the phase conductor C of the regulated circuit) is energized through a current transformer 38 by a measure of the current Ib acting in conductor B of the regulated circuit.

The effect of the illustrated connections is shown by the vector diagram of Fig. 2 in which the three voltages Ebb, Ebb and Em supplied through transformers I6 and corresponding to those acting in the regulated circuit at the point of transformer connection, are shown as forming the basic triangle A--B-C. At 100% power factor, the currents flowing in the regulated circuit conductors have the relative phase positions indicated by vectors Ibi, Ibi and Ibi.

In energizing compensator 22, current Ici causes the reactor element 30 to introduce into the regulator control supply circuit a voltage component RIci and the resistor element 2B to similarly introduce a voltage component XIci. The reactor 30 is so designed that the output voltage RIC leads by the energizing current Ic. The output connections from the resistor 26 of this compensator are reversed for a purpose later to be explained.

Likewise, the energizing current Ibi flowing from the secondary winding of the current transformer 38 through the elements of compensator 24 causes the reactor 30 to introduce into the regulator control supply circuit conductor 36, a voltage component RIbi and the resistor 26 to introduce a modifying component XIbi which leads by 90 the compensator energizing current Ibi. The output connections of both elements of this compensator are reversed in order that the compensating voltage components may properly combine in the manner indicated in Fig. 2.

As a result of the introductions above named, the potentials impressed upon the interconnected rectifiers I 3 are modified to the extent represented by the broken line triangle consisting of vectors Eab, E'bc and Eca. It will be noted that this triangle is also symmetrical and in effect consists of the basic or original triangle A--B-C having its sides all similarly modified as to magnitude and rotated slightly about the point A.

It will thus be seen that for the power factor load conditions above assumed, a balanced line-drop compensation for the threephase potentials has been effected in a manner entirely equivalent from a performance standi point to that resulting from the use of three single phase compensator assemblages. The improved connection of my invention by requiring only two of these assemblages thus reduces the total cost to two-thirds.

The balanced operation is also preserved for load currents of other power factors. For example, when the phase currents lag the corresponding voltages of the regulated circuit by 90, a condition representative of Zero percent power factor, they occupy phase positions represented in Fig. 2 by the vectors Ian, Ibb and Icb. As a result of this shifting, the modifying potentials so combine as to produce resulting voltages for impression upon the rectiiiers I8 which are represented in Fig. 2 by the vectors Ebb, E"bb and Eba. It will be noted that the dotted triangle thus formed is also symmetrical, the change in magnitude of all three of its sides being equal and it being shifted in the opposite direction around the point A.

If desired, a reactor 4U may be connected in the manner shown in the remaining or third conductor 42 of the regulator control supply circuit for the purpose of securing a slightly more s windings of the compensators 22 and 24 which the current supplied to the regulator control device by transformers I produces.

It will, therefore, be apparent that the system of my invention functions at all times to provide the desired balance in all three phases of its 1;

compensation. Because of the substantial savings in equipment cost before pointed out, it constitutes an exceedingly practical expedient.

It may furthermore be used in a wide variety of regulator control and other comparable applications of wiiic the system. represented in Fig. 1 is merely ilustrative. For example, equipment I0 may instead of being an induction or other type of feeder circuit voltage regulator be in the form of a generator voltage regulator of the rheostatie, vibratory, electronic-tube or any other equivalent type the supply circuit of which requires that there be impressed t. ereon a three phase control potential uniformly compensated for the lin-e drop in all three of the phases of the regul lated circuit. Application is thus not restricted to situations in which a group of rectifiers (I8) are interposed between the control element or device (I2) and the source of control potential supply.

il I) Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the scope of the appended claims.

I claim as my invention:

1. In combination with a three-phase power circuit, means for adjusting the voltage of said power circuit having a voltage responsive element, a control circuit for impressing a voltage upon said voltage responsive element that is a measure of the voltages acting in all three phases of said circuit, a system of line-drop compensation comprising a compensator connected in each of two of the phases of said control circuit, and means for circulating a current through each of said compensators that is a measure of the power current in that phase of the power circuit with which the other of said compensators is associated.

2. In combination with a three-phase power circuit, means for adjusting the voltage of said power circuit having a voltage responsive element, a control circuit for impressing a voltage upon said voltage responsive element that is a measure of the voltages acting in all three phases of said circuit, a system for producing balanced line-drop compensation comprising resistance and reactance compensator elements connected in each of two of the phases of said control circuit, and means for circulating a current through each pair of compensator elements that is a measure of the power current in that phase of the circuit with which the other pair of said elements is associated.

3. In combination with a three-phase power circuit, means for adjusting the voltage of said power circuit having a voltage responsive element, a control circuit for impressing a voltage upon said voltage responsive element that is a measure of the voltages acting in all three phases of said circuit, a system of line-drop compensation comprising a resistance and reactance compensator elements connected in each of two of the phases of said control circuit, and means for circulating a current through each of said compensator elements that are a measure of the power current in that phase of the circuit with which the other pair o said compensators is associated, said compensator connections being such that balanced compensation results for varying conditions of circuit load and power factor.

fi. A system of balanced line-drop compensation for a voltage responsive element connected to be energized from a three-phase circuit comprising, in combination with means for impressing upon said Voltage responsive element measures of the voltages acting in all three phases thereof, a compensator connected in each or" two of the phases of said control-supply means, and means for circulating a current through each of said compensators that is a measure of the power current in that phase of the circuit with which the other of said compensators is associated.

5. A system of balanced line-drop compensation for a voltage responsive element connected to be energized from a three-phase circuit comprising, in combination with means for impressing upon said voltage responsive element measures of the voltages acting in all three phases thereof, a resistance-drop compensating element connected in each of two of the phases of said control-supply means and means for energizing each of said elements by a measure of the power current in that phase of the circuit with which the other of said compensators is associated.

6. A system oi balanced line-drop compensation for a voltage responsive element connected to be energized from a three-phase circuit comprising, in combination with means for impressing upon said voltage responsive element measures of the voltages acting in all three phases thereof, a reactance-drop compensating element connected in each of two of the phases of said control-supply means and means for energizing each of said elements by a measure of the power current in that phase of the circuit with which the other of said compensators is associated.

7...A system of balanced line-drop compensation i'or a voltage responsive element connected to be energized from a three-phase circuit comprising, in combination with means for impressing upon said voltage responsive element measures of the voltages acting in all three phases thereof, reactance and reactance drop compensating elements connected in each of two of the phases of said control-supply means, and means for energizing each oi said element pairs by a measure of the power current in that phase o1' the power current with which the other of said element pairs is associated.

8. In combination, a main electrical circuit having three phase conductors, a supply circuit having three conductors corresponding to the respective main circuit conductors, voltage responsive means connected to be energized in accordance with the summation of the voltages between the several pairs of said phase conductors, line drop compensating means connected in crcuit with each of two of said three supply conductors and each comprising means for introducing voltage components into one of said supply circuit conductors that is a measure of the ohmic line drop and the reactive line drop, respectively, in the main circuit conductor corresponding to the other of said two supply conductors.

9. In compisation, a main electrical circuit having three phase conductors, voltage responsive means, a three conductor supply circuit for energizing said voltage responsive means in accordance with the summation of the voltages between the several pairs of phase conductors of said first named circuit, line drop compensating means connected in each of two of said three supply conductors and comprising means for introducing a voltage component into each of said supply conductors that is responsive to the ohmic component oi line drop in the main phase conductor corresponding to the other of said supply conductors, and means for introducing a voltage component into each of said supply conductors that is responsive to the reactive component of line drop in the main phase conductor corresponding to the other of said supply conductors.

10. In combination, a three phase power circuit, a voltage responsive device, a supply circuit having three conductors corresponding to the respective conductors of the three phase power circuit for energizing said voltage responsive device in accordance with the summation of the voltages between the several pairs of phase conductors, line drop compensators connected in each of two of sai-d supply circuit conductors and each including a reactor element and a resistor element, and means for circulating a current through each of said compensators that is a measure of the current in the power circuit phase conductor with which the other compensator is associated.

11. In combination, a three phase power circuit, a voltage responsive device, a supply circuit having three conductors corresponding to the respective conductors of the three phase power circuit for energizing said voltage responsive device in accordance with the summation of the voltages between the several pairs of phase conductors, line drop compensators connected in each of two of said supply circuit conductors and each including a reactor element and a resistor element, means for circulating a current through each of said compensators that is a measure of the current in the power circuit phase conductor with which the other compensator is associated, and a reactor in the third supply circuit conductor.

12. In combination, a three phase power circuit, a voltage responsive device, a supply circuit having three conductors corresponding to the respective conductors of the three phase power circuit for energizing said voltage responsive device in accordance with the summation of the voltages between the several pairs of phase conductors, line drop compensators for introducing compensating voltage components into each of two of said supply circuit conductors and each including a reactor element having primary and secondary windings coupled to effect a substantially 90 voltage phase shift, and a resistor element comprising an insulating transformer having primary and secondary windings and a resistor connected in shunt relation to said primary winding, the secondary windings of the compensator elements being connected in series in their respective supply circuit conductors, and means for circulating a current through the primary windings of said compensator elements that is a measure of the power current in that phase of the power circuit corresponding to the other of said two supply circuit conductors.

IVAN D. APPLEGATE. 

